Dehydration of saturated nitriles



Nov. 9,-1948. J. w; TE'Tl-:R ETAL DEHYDRATION'OF SATURATED NITRILES Filed Oct. 12. 1944 mJEtz E254 SPDM mut; v

enterre daarnaartoe or estimaron uraltes .lohn W. 'lleter and Walter li. lf/ierwin, Chicago, lll., assigner-s to Sinclair Benning Company, New Yorlr, N. if., a corporation ci Maine Application October 12, 194e, Serial No. 558,475

i Claim. (Cl. 20E- 60) il e This invention relates to the dehydration oi ylene chloride, the nitrlle and the remainder ci. saturated nitriles containing 2 to 4 carbon atoms, the Water. The bottom layer may then be subthat is, acetcnitrile, proplonitrile and normal jeeted to a close fractional distillation, in a fracand iso butyronitriles, whereby` anhydrous or tional distillation aonefrorn which an azeotropic substantially dehydrated products may be ob- E; mixture of the` methylene chloride and water is tained hy direct fractional distillation ci the reremoved as an overhead fraction. The fractional spective nitriles contaminated by water. distillation operation may be of either the con- Dehydration of these nitriles has presented a tinuous or batch type and therefore the dry dlihcult problem because each'oi them forms a v'nltrile may be removed from the fractional disbinary azeotrope with water. lo tlllatlon zone either as an overhead product or as We have discovered that if methylene chloride a bottoms fraction. be added to a" saturated nitrile containing 2 to 4 The invention will be further illustrated by the carbonl atoms the methylene chloride will form following specic example but it is not limited an azeotrope with thewater present but will not thereto: form. to kany substantial extent at least, either To departs by weight of acetonitrile containa binary azeotrope with the nltrile or a ternary ing 16% by weight of waterv was added 409 parts azeotrope with the nitrile and water. by weight of methylene chloride. The resulting Utilizing this peculiarity of methylene chloride mixture was cloudy, and when permitted to in the presence o! the lower saturated nltrlles stand, an upper water layer separated. In this and water, the process of the present invention 20 way '1.3 parts of an upper water layer were: sepacomprises the addition of methylene chloride rated. corresponding to almost 70% of the water to the water-contaminated nltrile and subjecting originally present in the acetonitrile. The bottom the mixture to close fractional distillation wherelayer was subjected Vto, close fractional distillaby the water is carried ofi by the methylene chlotion. The distillation temperature gradually rose ride leaving behind a substantially anhydrous from 37 C at thebeginning ofthe distillation nitrile. 1 to 38 C. when"11% by volume oi the charge had The invention is also applicable to an opera.- been distilled oi.v It then rose` sharply to 81 C. tion whereby the entire charge is fractionally dlsat something under,A 80% by volume oir and retilled and contemplates either batch 'or continumained constant until 89% of the charge had ous operation. The operation may include the been distilled oil at which-polnt'the distillation distillation o! the nltrlle, or only the distillation was discontinued. The fraction distilled ofi' at of the water-methylene chloride mixture there- 31 C. was substantially pure, dry acetonltrile. flOm- The other'saturated nitriles having 2 to 4 car- The optimum proportion of methylene chloride bon atoms. namely propionltrile and normal and to be added will depend largely upon the amount lso butyronltrlle. contaminated with water, may4 of water to be removed. It has been found that lt with advantage be dehydrated by the sam-e genrequ-ires about 19 lbs. of methylene chloride to eral procedure without material loss of the nitrile carry ofi, as an ezeotrope,.1 lb. o! water. Howi1-contamination ofthe nitrlle product by methever. it does not lfollow that this quantity of ylene chloride` methylene chloride need be added to remove the 40 We claim:

water from a water-contaminated saturated A process fOr the dehydl'atiOn f Saturated l lower nitrile, because it the nitrlle contains rela.- nitriles of 2 to4 carbon atoms per molecule which' tively large proportions of water, for example. comprises adding methylene chloride to a. hya'cetonitrile with 16% or more water, addition drous nitrlle, subiectingthe mixture to stratifiof the methylene chloride will result in separa- 45 cation to separate -an aqueous upper layer. and tion of an aqueous layer, which may be separated fractionally distllling the water and methylene by decantatlon or the like and need not be rechloride from the lower layer` as a. binaryazeomoved'by distillation. For completedehydration trope. of a, nitrile, somewhat more than the theoretical y JOHN W. TETER. proportion of 19 lbs. of methylene chloride to 50 WALTER. J. MERWIN. each pound of water to be removed by dlstillai tion' should be used.v RE'Fl-I RIENCESI A embodiment 0f the process "f the invention The following references .are of record in the is illustrated .in-diagrammatic tormin the accom- ,me of this patent: panying drawing. In carrying out the embodiment of my invention as illustrated in the draw- UNITED STATES, PATENTS ing the water contaminated saturated lower Number Name Date nitrilev to bef dehydrated andmethylene chloride 2,263,436 Brlttonet al Nov. 18, 1941 are supplied to a zone wherein stratlcation is 2,305,106 Pratt -j -o Dec. 15, 1942 permitted with resultant formation 4of-an aqueous 60 2,404,163 Carpenter July 16, 1946 upper layer and a bottom layer comprising meth- 

